This invention relates to improvements in or relating to thrust bearing devices used with vertical turbines, vertical pumps, vertical turbine-generators, etc., and, more particularly, to improvements in or relating to a thrust bearing device for a machine of high capacity provided with a plurality of bearing shoes of a segmental shape arranged around a rotary shaft and resiliently supported for free pivotal movement.
As is well known, a thrust bearing device of the aforementioned type generally for bearing thrust loads, is provided with a plurality of bearing shoes arranged around a rotary shaft which are each usually supported at one point by a bolt having a spherical head or by a spring also having a spherical head, to meet the requirement that a bearing oil film should be formed on each bearing shoe.
Bolts and springs are used each for supporting one of the plurality of bearing shoes in order that the same thrust load may be carried by all the bearing shoes. In support means using bolts, the heights of the bolts can be adjusted as desired to bring the sliding surfaces of all the bearing shoes to the same level. The use of the springs enables, when the sliding surfaces of the bearing shoes become slightly unbalanced in height, the condition to be compensated for by the resilience of the springs.
The most important thing for this type of bearing device is that a uniform oil film be formed between the rotary member and the sliding surfaces of the bearing shoes at all times. To attain this end, support means for the bearing shoes should be constructed such that it is possible to adjust the heights of the sliding surfaces of the bearing shoes so that no particular bearing shoes may have concentrated thrust loads applied thereto and that the bearing shoes can move independently on their own accord.
The higher the load applied to a machine or the higher the capacity of a machine, the higher accuracy is required in adjusting the heights of the bearing shoes. For this reason, it has been usual practice to use springs that can be adjusted for the support means for the thrust bearing device used with a machine of high capacity.
In, for example, Japanese Utility Model Publication No. 8805/68, one type of support means adopted for use with a machine of high capacity is proposed which is regarded as being relatively effective, wherein each bearing shoe is supported by a resilient underlying pressure receiving member formed on its upper surface with a projection for supporting the bearing shoe and on its undersurface with legs each located at one of opposite ends thereof.
The above-noted support means can perform its function without any trouble when used for supporting bearing shoes for journaling an ordinary rotary member. However, when this support means is used for supporting bearing shoes for journaling the rotary member of a machine of high capacity, it is necessary to increase the strength of resilient underlying pressure receiving members because of the high load applied thereto. The end of increasing the strength of the underlying pressure receiving members might be attained by increasing the width or thickness of each underlying pressure receiving member or using material of higher strength for forming each underlying pressure resisting member. However, since the underlying pressure receiving members cannot perform their function satisfactorily unless they are resilient to a certain extent and, in view of the fact, that available space is limited, it is difficult to readily solve the problem. Generally, the pressure receiving members are flexed about 1 mm. If the length of each pressure receiving member is increased to suit the condition of use with a machine of high capacity in a limited range, difficulties would be experienced in allowing for the flexing of 1 mm.